The purpose of this project is to study the physical properties of a wide variety of biological macromolecules, with the goal of correlating these properties to the structure and function of the macromolecules. The emphasis is on the thermodynamics of the interactions of these macromolecules and on their molecular size and shape. Analytical ultracentrifugation and mathematical modeling are the principal research techniques used. Studies on actin have been directed toward investigating the interaction of actin with actobindin. Studies on the interleukin2 receptor have been directed to establishing the monomer molecular weight, and determining whether or not it has aggregative properties. Studies on the human platelet glycoprotein GPIIb/IIIa have been directed toward studying its interaction with fibrinogen. Studies of various deoxynucleotides have been directed toward investigating the thermodynamics of the reversible monomer-dimer equilibrium as a function of structure,. Studies on HIV reverse transcriptase have been directed toward investigating the thermodynamics of the homogeneous association of the P66 subunit and the heterogeneous association of P66 with the P51 subunit. Studies on chromagranin A have been directed toward investigating the effects of pH and calcium ion concentration on the aggregative properties of the molecule.